krb5 commit: Track preauth failures instead of tries
Greg Hudson
ghudson at mit.edu
Thu Feb 2 15:38:42 EST 2017
https://github.com/krb5/krb5/commit/a1dc81d22304e77edaa8388c7d7d75cade81dc80
commit a1dc81d22304e77edaa8388c7d7d75cade81dc80
Author: Greg Hudson <ghudson at mit.edu>
Date: Fri Jan 13 12:16:04 2017 -0500
Track preauth failures instead of tries
In preauth2.c, instead of noting whenever we try a real preauth mech,
note when a mechanism fails on our side. Tracking only failures
eliminates the need to reset the list for multi-step preauth exchanges
or for processing padata in the AS-REP, but we will need the function
later for continuing after optimistic preauth failures.
ticket: 8537
src/lib/krb5/krb/get_in_tkt.c | 3 --
src/lib/krb5/krb/int-proto.h | 3 ++
src/lib/krb5/krb/preauth2.c | 65 +++++++++++++++++++++++-----------------
3 files changed, 40 insertions(+), 31 deletions(-)
diff --git a/src/lib/krb5/krb/get_in_tkt.c b/src/lib/krb5/krb/get_in_tkt.c
index e48ade1..99d843e 100644
--- a/src/lib/krb5/krb/get_in_tkt.c
+++ b/src/lib/krb5/krb/get_in_tkt.c
@@ -1514,8 +1514,6 @@ init_creds_step_reply(krb5_context context,
code = restart_init_creds_loop(context, ctx, FALSE);
} else if ((reply_code == KDC_ERR_MORE_PREAUTH_DATA_REQUIRED ||
reply_code == KDC_ERR_PREAUTH_REQUIRED) && retry) {
- /* reset the list of preauth types to try */
- k5_reset_preauth_types_tried(ctx);
krb5_free_pa_data(context, ctx->preauth_to_use);
ctx->preauth_to_use = ctx->err_padata;
ctx->err_padata = NULL;
@@ -1565,7 +1563,6 @@ init_creds_step_reply(krb5_context context,
goto cleanup;
/* process any preauth data in the as_reply */
- k5_reset_preauth_types_tried(ctx);
code = krb5int_fast_process_response(context, ctx->fast_state,
ctx->reply, &strengthen_key);
if (code != 0)
diff --git a/src/lib/krb5/krb/int-proto.h b/src/lib/krb5/krb/int-proto.h
index f6f4f2f..57411a9 100644
--- a/src/lib/krb5/krb/int-proto.h
+++ b/src/lib/krb5/krb/int-proto.h
@@ -199,6 +199,9 @@ k5_free_preauth_context(krb5_context context);
void
k5_reset_preauth_types_tried(krb5_init_creds_context ctx);
+krb5_error_code
+k5_preauth_note_failed(krb5_init_creds_context ctx, krb5_preauthtype pa_type);
+
void
k5_preauth_prepare_request(krb5_context context, krb5_get_init_creds_opt *opt,
krb5_kdc_req *request);
diff --git a/src/lib/krb5/krb/preauth2.c b/src/lib/krb5/krb/preauth2.c
index 354234a..17f2133 100644
--- a/src/lib/krb5/krb/preauth2.c
+++ b/src/lib/krb5/krb/preauth2.c
@@ -54,7 +54,7 @@ struct krb5_preauth_context_st {
struct krb5_preauth_req_context_st {
krb5_context orig_context;
- krb5_preauthtype *tried;
+ krb5_preauthtype *failed;
krb5_clpreauth_modreq *modreqs;
};
@@ -201,11 +201,7 @@ cleanup:
free_handles(context, list);
}
-/*
- * Reset the memory of which preauth types we have already tried, because we
- * are entering a new phase of padata processing (such as the padata in an
- * AS-REP).
- */
+/* Reset the memory of which preauth types we have already tried. */
void
k5_reset_preauth_types_tried(krb5_init_creds_context ctx)
{
@@ -213,10 +209,27 @@ k5_reset_preauth_types_tried(krb5_init_creds_context ctx)
if (reqctx == NULL)
return;
- free(reqctx->tried);
- reqctx->tried = NULL;
+ free(reqctx->failed);
+ reqctx->failed = NULL;
}
+/* Add pa_type to the list of types which has previously failed. */
+krb5_error_code
+k5_preauth_note_failed(krb5_init_creds_context ctx, krb5_preauthtype pa_type)
+{
+ krb5_preauth_req_context reqctx = ctx->preauth_reqctx;
+ krb5_preauthtype *newptr;
+ size_t i;
+
+ for (i = 0; reqctx->failed != NULL && reqctx->failed[i] != 0; i++);
+ newptr = realloc(reqctx->failed, (i + 2) * sizeof(*newptr));
+ if (newptr == NULL)
+ return ENOMEM;
+ reqctx->failed = newptr;
+ reqctx->failed[i] = pa_type;
+ reqctx->failed[i + 1] = 0;
+ return 0;
+}
/* Free the per-krb5_context preauth_context. This means clearing any
* plugin-specific context which may have been created, and then
@@ -291,7 +304,7 @@ k5_preauth_request_context_fini(krb5_context context,
TRACE_PREAUTH_WRONG_CONTEXT(context);
}
free(reqctx->modreqs);
- free(reqctx->tried);
+ free(reqctx->failed);
free(reqctx);
ctx->preauth_reqctx = NULL;
}
@@ -612,28 +625,17 @@ pa_type_allowed(krb5_init_creds_context ctx, krb5_preauthtype pa_type)
pa_type == ctx->allowed_preauth_type;
}
-/*
- * If pa_type has already been tried as a real preauth type for this
- * authentication, return true. Otherwise ass pa_type to the list of tried
- * types and return false.
- */
+/* Return true if pa_type previously failed during this authentication. */
static krb5_boolean
-already_tried(krb5_init_creds_context ctx, krb5_preauthtype pa_type)
+previously_failed(krb5_init_creds_context ctx, krb5_preauthtype pa_type)
{
krb5_preauth_req_context reqctx = ctx->preauth_reqctx;
size_t i;
- krb5_preauthtype *newptr;
- for (i = 0; reqctx->tried != NULL && reqctx->tried[i] != 0; i++) {
- if (reqctx->tried[i] == pa_type)
+ for (i = 0; reqctx->failed != NULL && reqctx->failed[i] != 0; i++) {
+ if (reqctx->failed[i] == pa_type)
return TRUE;
}
- newptr = realloc(reqctx->tried, (i + 2) * sizeof(*newptr));
- if (newptr == NULL)
- return FALSE;
- reqctx->tried = newptr;
- reqctx->tried[i] = pa_type;
- reqctx->tried[i + 1] = ENCTYPE_NULL;
return FALSE;
}
@@ -665,8 +667,8 @@ process_pa_data(krb5_context context, krb5_init_creds_context ctx,
/* Make sure this type is for the current pass. */
if (clpreauth_is_real(context, h, pa->pa_type) != real)
continue;
- /* Only try a real mechanism once per authentication. */
- if (real && already_tried(ctx, pa->pa_type))
+ /* Don't try a real mechanism again after failure. */
+ if (real && previously_failed(ctx, pa->pa_type))
continue;
mod_pa = NULL;
ret = clpreauth_process(context, h, modreq, ctx->opt, &callbacks,
@@ -694,6 +696,12 @@ process_pa_data(krb5_context context, krb5_init_creds_context ctx,
/* Save the first error we get from a real preauth type. */
k5_save_ctx_error(context, ret, &save);
}
+ if (real && ret) {
+ /* Don't try this mechanism again for this authentication. */
+ ret = k5_preauth_note_failed(ctx, pa->pa_type);
+ if (ret)
+ goto cleanup;
+ }
}
}
@@ -944,9 +952,10 @@ k5_preauth_tryagain(krb5_context context, krb5_init_creds_context ctx,
TRACE_PREAUTH_TRYAGAIN(context, h->vt.name, pa_type, ret);
if (!ret && mod_pa == NULL)
ret = KRB5KRB_ERR_GENERIC;
- if (ret)
+ if (ret) {
+ k5_preauth_note_failed(ctx, pa_type);
return ret;
-
+ }
for (count = 0; mod_pa[count] != NULL; count++);
ret = copy_cookie(context, err_padata, &mod_pa, &count);
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